Congrats! I am currently rank 46 and having trouble beating the Frost Dragon in the Colosseum.
What team did you beat it with?
Lasswell/Artemios/Kefka/Tellah/Lenna
Observations:
-- Fira, preferably Firaga element chain between two (or more casters) is more damaging and more efficient than Kefka using Hyperdrive.
-- Keep the dragon power broken at all times (Ifrit).
-- Create a designated "tank", stack him with HP mods. On the turn that you silence it, taunt the dragon with the tank unit (Provoke, Golem). Otherwise very bad things will happen, especially if it is not power broken.
-- For the love of moogles, count the turns that the dragon is debuffed. On the third turn of a debuff, start applying a new debuff of a different type. Bad things happen if the dragon can break free of all debuffs.
-- Generally speaking, Cheer isn't worth it for the fight. It is too much of a mana drain for long protracted fights.
-- If you do not have Lenna for Esuna, remember to love tap a confused unit with one of the mages.
-- At the barest minimum 2x Cura, or Curaja (3 Curas or Curaja + Cura) needed if not power broken) across two units is really needed to keep up with damage. Krille can help with that because of dual cast, but her HP is a real liability.
-- Bad things will happen just because of RNG. Tellah's raise is huge in giving the team a second chance when the dragon decides to focus all three melee attacks in a round on a squishy unit.
In my run, about everything wrong that could happen did happen. Lost Artemios to a bad RNG melee round. Lasswell kept being confused and decided to "enhance" the complexion of my mages with his new and shiny sword multiple times during the fight. I barely squeaked through the fight as a result. It could have gone much, much better than it did. But, only have to win exactly once ever, and that is just fine with me.